1. Field of the Invention
The present invention is directed to a microwave frequency chip resistor assembly and, more specifically, to a chip resistor for terminating unused transmission lines to avoid interference with other signals.
2. Description of Related Art
As the TV industry uses more and more Serial Digital Data Signals for transmitting Television Signals and moves closer to a practical HDTV system, unterminated transmission lines must be terminated or risk interfering with other signals in the system.
Video jacks are commonly used switches in television studio master control rooms and editing suites. With the advent of Serial Digital techniques, unused signals in the switches must be terminated or risk interfering with the other transmission lines within the jack due to the high data rates. Conventionally, standard metal film resistors have been used as the terminating device.
In order to minimize reflections, the standard metal film resistor is soldered into a cylindrical housing of dimensions that provide a matched impedance (typically 75 ohms). As shown in FIG. 1, standard metal film resistor A is soldered in place at points B and C within housing D. This assembly is then installed in the video jack. A problem occurs because at microwave frequencies of 1 Ghz and above, variations in the reactance of the standard metal film resistor are significant. Typical metal film resistors are laser trimmed by etching a spiral groove in the body of the resistor to achieve a desired resistance. This causes variation in inductance due to the laser trimming and results in a need to vary the housing dimensions.
Additionally, soldering is a time-consuming operation that requires skilled operators, and the process requires cleaning of the assembly after the soldering process. Also, the variation of inductance in the metal film resistor causes unreliable microwave performance.